System and method for remote inspection of liquid filled structures

ABSTRACT

A system and method for remote inspection of a liquid filled tank or structure is disclosed. In the system, a remotely operated underwater vehicle is deployed in a liquid filled tank which includes pre-installed location identifier tags. The remotely operated underwater vehicle includes at least one camera for providing a video feed to an operator. The remotely operated underwater vehicle is piloted through tanks to be inspected, scanning tags and transmitting video and sensor data to the operator via operator&#39;s computer. The operator inspects and records observations of the video and sensor data to the system. Resulting data is recorded and reports generated.

RELATED APPLICATIONS AND INCORPORATION BY REFERENCE

The foregoing applications, and all documents cited therein or during their prosecution (“appln cited documents”) and all documents cited or referenced in the appln cited documents, and all documents cited or referenced herein (“herein cited documents”), and all documents cited or referenced in herein cited documents, together with any manufacturer's instructions, descriptions, product specifications, and product sheets for any products mentioned herein or in any document incorporated by reference herein, are hereby incorporated herein by reference, and may be employed in the practice of the invention. More specifically, all referenced documents are incorporated by reference to the same extent as if each individual document was specifically and individually indicated to be incorporated by reference.

FIELD OF THE INVENTION

This invention relates to the inspection of structures that house, store or transport liquid. In some instances, such inspection can occur without removing the liquid from the structure.

BACKGROUND OF THE INVENTION

A double-hull is a ship hull design and construction method where the bottom and sides of the ship have two complete layers of watertight hull surface: one outer layer forming the normal hull of the ship, and a second inner hull which is some distance inboard, typically by a few feet, which forms a redundant barrier to seawater in case the outer hull is damaged and leaks. The space between the two hulls is sometimes used for storage of fuel or ballast water.

Double-hulls are a more extensive safety measure than double bottoms, which have two hull layers only in the bottom of the ship but not the sides. Double-hulls' ability to prevent or reduce oil spills led to their being standardized for other types of ships including oil tankers by the International Convention for the Prevention of Pollution from Ships or MARPOL Convention. Double-hulls often include anti-slosh baffles or partial bulkheads.

Classification societies, which establish and maintain technical standards for the construction and operation of ships and offshore structures, validate that construction is according to these standards and carry out regular surveys in service to ensure compliance with the standards. Classification surveyors inspect ships to make sure that each inspected ship, its components, and machinery are built and maintained according to the standards required for the ship's class. Such classification societies require periodic thorough inspection of such double-hull tankers in the presence of a classification surveyor.

The tendency then, when double-hull tankers meeting the above regulations were first designed, was to use the voids between the inner and outer hull of the tanker as ballast water tanks. The ballast tank essentially was formed down the sides of the tanker and across the bottom in a “U” shape. One variant of the “U” shape was made by inserting a bulkhead at the center of the “U” in the bottom of the tanker, thus creating two J-shaped tanks. Frequent and thorough inspection of ballast tanks is important because of the corrosive nature of the sea water used as ballast and because ballast water is typically loaded into ballast tanks while the tanker is in port, where the water tends to have a high degree of silt, causing the bottom of the ballast tanks to accumulate mud.

A common method of inspecting these types of tanks of certain sizes is for inspectors to float in a raft inside the tank, starting while the tank was nearly full, and floating around to inspect the sides of the tank. The water would slowly be pumped out of the tank, gradually exposing more of the sidewalls to the inspectors. This method, called rafting, is easy to implement, and it was thorough since there was access to the entire depth of the tank.

While the initial design of double-hull tankers is simple and intuitive, there are many problems associated with it. One problem is that the deep and narrow shape of the ballast tanks makes inspection, maintenance and repair difficult. Because of the desire to utilize as much space as possible for cargo, the width of the void between the inner and outer hull in double-hull tankers is minimized as much as can be consistent with the requirements of the regulations and the volume of ballast needed. For example, under U.S. and international regulations, the width between the inner and outer hull can be as small as two meters. The ballast tank, therefore, is relatively narrow and deep, extending from the top of the ship all the way down and across the bottom of the tanker. Thus, ballast tanks are often inspected dry because of the narrow confines of the ballast tanks.

Additionally, the surfaces in the ballast tank can be slippery, making inspection even more difficult. As discussed above, since ballast water taken in while a tanker is in port may contain silt, the surfaces of the ballast tank may become coated with mud. The tight space and other structural constraints severely limit the ability to construct inspection aids, such as walkways, to ease the difficulties of inspection. In addition, the nature of the space blocks all natural light from these spaces and, because it is filled with water when in use, there can be no permanent electrical light fixtures in the ballast space. Other types of manual inspection, including walking or otherwise rigging a human for manual inspection is both dangerous and inefficient, requiring significant manpower and time commitments, including tank evacuation, gas freeing, testing, certification, safety and standby-requirements. Currently, humans measure the thickness of ballast tank walls using NDT Ultrasonic Thickness Gauges.

Examples of double-hull tankers are illustrated in such publications as U.S. Pat. Nos. 5,158,031 and 5,901,656 and U.S. Published Patent Application No. 2002/0152942.

Referring now to FIGS. 1-3, which are not to scale, a conventional double-hull tanker 10 is shown. The double-hull includes an outer side hull 12 and an inner side hull 14 (not shown in FIG. 1), as well as an outer bottom hull 16 and an inner bottom hull 18. One or more cargo tanks 20 are contained within the inner side hull 14 and the inner bottom hull 18. A plurality of ballast tanks 22 are formed in the space between the inner side hull 14 and outer side hull 12 and between the inner bottom hull 18 and outer bottom hull 16. Bulkheads 24, which may extend to the ballast tanks, separate the space created within the inner side hull 16 and inner bottom hull 18 into compartments, resulting in the cargo tanks 20. Longitudinal bulkheads 26 and 28 may be installed to create two or more cargo tanks 20 and may extend to the ballast tanks 22. The ballast tanks may be further separated by decks or ‘tween decks,’ floors 30 parallel to the vessel's main deck. In this arrangement, the space between the inner hull (14 and 18) and the outer hull (12 and 16) is configured to load saltwater ballast. The Ballast tanks are typically steel tanks, and run the length of the ship's hull. They function as a double-hull, or hull within a hull and they leave a void between the outer skin of the boat, and the inner skin of the boat.

FIG. 4, which is not to scale, illustrates exemplary ballast tank compartments 22 a of ballast tanks 22. Typically, ballast tanks at a lower level of the double-hull tanker 10 are accessed through a series of ladders 32 and manholes or access panels 34 from the top of the tank 10 to the bottom. Access between ballast tank compartments on the same level are accessed by openings or baffles (called lightning holes) (not shown) in the bulkheads 24, 26 that separate the compartments or tanks. Lower compartments may also be accessed through access panels in the floors of the ballast tank compartments.

The tanks are typically steel or stainless steel walled, and the walls within the tanks may be coated with an industrial corrosion resistant paint. When the corrosion resistance is damaged, the tanks corrode and the result is rust. Tanks are also a low oxygen environment. Rust is caused by oxidation, which is the reaction between steel and air. The result is rust, which is Fe₂O₃ (Ferris trioxide). Because the iron in the steel combines with the oxygen to form the rust, the oxygen in the tank is converted, and the overall quantity of oxygen in the tank decreases. Therefore, because the oxygen available in the tank is consumed in this process, the tanks are generally low oxygen environments, which are harsh on the human body.

Citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention.

SUMMARY OF THE INVENTION

The present invention is directed to a system and method for remote inspection of liquid filled structures.

In one aspect of the present invention, a system for inspecting a liquid filled structure includes at least one submersible identification tag fixed to a fixture within the liquid filled structure; a remotely-operated underwater vehicle (ROV), the ROV including: a video camera mounted on the ROV; a transmitter for transmitting video image data from the ROV; and an operator terminal including display screen, the operator terminal in operable communication with the ROV.

In the system the ROV may further include at least one additional sensor, wherein the at least one additional sensor is one of a ultrasonic thickness gauge, cathodic potential gauge, magnetic particle testing, radiographic testing method, ultrasonic shearwave testing method, video location device, salinometer, 3-D laser scanner, long base line positioning sensor, ultra short baseline positioning sensor, and scanning sonar positioning sensor.

In another aspect of the present invention, a method for inspecting a liquid filled structure, includes the steps of: deploying a remotely-operated underwater vehicle (“ROV”) in the liquid filled structure; generating a video signal via a video camera mounted on the ROV; piloting the ROV through locations within the liquid-filled structure; reading at least one submersed identification tag fixed within the liquid filled structure to provide an identification code; correlating the identification code with a location within the structure; displaying video from the video signal on an operator terminal; and inspecting at least one fixture within the liquid-filled structure displayed on the operator terminal and determining a rating for the fixture.

It is noted that in this disclosure and particularly in the claims and/or paragraphs, terms such as “comprises”, “comprised”, “comprising” and the like can have the meaning attributed to it in U.S. Patent law; e.g., they can mean “includes”, “included”, “including”, and the like; and that terms such as “consisting essentially of” and “consists essentially of” have the meaning ascribed to them in U.S. Patent law, e.g., they allow for elements not explicitly recited, but exclude elements that are found in the prior art or that affect a basic or novel characteristic of the invention.

Further embodiments, features, and advantages of the system and methods for remote inspection of liquid filled structures, as well as the structure and operation of the various embodiments of the same are described in detail below with reference to the accompanying drawings. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, which are incorporated herein and form part of the specification, illustrate a container handle. Together with the description, the figures further serve to explain the principles of the container handle described herein and thereby enable a person skilled in the pertinent art to make and use the system and methods for remote inspection of liquid filled structures. The following detailed description, given by way of example, but not intended to limit the invention solely to the specific embodiments described, may best be understood in conjunction with the accompanying drawings.

FIGS. 1-4 illustrate an exemplary double-hull tanker.

FIG. 5 illustrates an embodiment of the present invention;

FIG. 6 illustrates a method according to an aspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to embodiments of the system and methods for remote inspection of liquid filled structures with reference to the accompanying figures, in which like reference numerals indicate like elements.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

The present invention will be further illustrated in the following Examples, which are given for illustration purposes only and are not intended to limit the invention in any way.

As illustrated in FIG. 5, the system of the present invention includes a remotely operated vehicle (“ROV”) 100. The ROV 100 includes at least one camera 106 capable of capturing video images which may be stored or transmitted, or both. The camera 106 may also be configured to capture still images, and store or transmit, or both, the captured still images. The camera 106 may be appropriately configured for low light conditions, including low light cameras using active infrared, large lenses, additional light, improved spectral range or technique to allow an operator to view images. The ROV 100 may include other information gathering devices or sensors 108, such as an ultrasonic thickness gauge, cathodic potential gauge, magnetic particle testing, radiographic testing method, ultrasonic shearwave testing method, RFID reader, video location device, salinometer, 3-D laser scanner, long base line positioning, ultra short baseline positioning, scanning sonar positioning, or other device to gather information as would be appreciated by one of skill in the art.

The ROV 100 is connected via wire or wirelessly to a computer 102 or other control device such as a tablet, smart phone or the like to be controlled by a pilot or operator. The ROV 100 includes a processor connected to a transmitter for transmitting data to the computer 102 and a receiver for receiving commands from the operator. The illustration in FIG. 5 is for purposes of explanation only. One of skill in the art would appreciate that the connection to the computer 102 may involve further connections rather than a direct “wire” to the laptop. The computer or control device 102 may include sufficient storage to store data captured by the ROV 100 or may be further connected by wire or wirelessly to a further storage and processing capabilities, such as “Cloud” storage/computing or other computer systems.

The ROV 100 further includes a code reader 110 capable of reading an optical machine readable code, such as a bar code, matrix bar code (two-dimensional bar code) such as a Quick Response (“QR”) Code or the like. Alternatively, the ROY 100 may include a radio-frequency identification (“RFID”) reader than receives radio frequency identifiers from RFID tags. The RFID reader may be an active or a passive reader, as appropriate for the RFID tags being read. For example, in situations where a battery cannot be used, such as hazardous environments, passive tags may be used. In other situations, an active tag may be used to power the internal sensors in a non-hazardous environment. In a further aspect of the invention, a visual tag, such as a bar code or a QR code can be read from the video feed or still photo by a reader located remotely from the ROV 100.

The ROV 100 may further include a storage medium thereon for storing data such as photos, video, and sensor data generated by the cameras and sensors on-board the ROV 100.

As illustrated in FIG. 5, the ballast tank compartment wall 12 a includes a machine readable code sign or RFID tag 104. The signs or tags 104 should be submersible and be made of material sufficient to withstand the salt water or other corrosive substance that might be stored in the compartment. As contemplated by the present invention, sufficient tags 104 may be affixed within the vessel 10 to provide sufficient location data to correlate to the area inspected. For example, in most instances, one sign or tag 104 per ballast compartment will be appropriate. In other instances, one sign or tag 104 per structure, wall or fixture may be selected. In addition to one tag per compartment, tags 104 may also be provided near sacrificial anodes, pumps, bell mouths, suction discharge piping, strainers, or any other required inspection concerns.

Sacrificial anodes are made from an alloy more “active” than that of the metal used in the ships construction. This allows the bulk of the corrosion to take place on the galvanic anode and not on the structural steel. This “sacrificial” anode is eaten away over time by electrolysis. These anodes must be inspected routinely so that they can be replaced before they are completely worn away. The failure to keep fresh anodes in place will result in increasingly rapid corrosion within the tank. These anodes are located throughout the tank and also on pump casings and pipeline suctions and discharges.

In addition, sensors 106 may be attached to the tank wall to measure the cathodic potential of the steel directly behind where the sensor is attached in addition to the ROV's thickness gauge. The cathodic potential sensors 106 may be collocated with the machine readable code sign. Additional cathodic potential sensors may be deployed within the tanks as appropriate, for example, at weld seams to measure the corrosion of metal, such as steel or weld material, within the tank. The ROV 100 may be configured to retrieve data from the cathodic potential sensor. Thus, the tank's corrosion can be tracked with the cathodic potential sensors and steel thickness tracked at various points on the tank wall. In addition, sensors of multiple types may be included to allow remote sensing for the acquisition of long term data at the request of a customer such as cathodic potential, salinity, temperature, organic compounds, oxygen, hydrocarbon, etc.

The ROV 100 uploads the data from the sensors, which records the data in the tank over time and puts the data into a program that generates a report based on the individual thickness measurements, and the sensor's recorded information. Together, the ROV 100 uploads the data from the sensors, which records the data in the tank over time and puts the data into a program that generates a report based on the individual thickness measurements, and the sensor's recorded information. The ROV may also upload video or still photos to the system, which may be included a report generated by the system.

The ROV 100 is of appropriate dimension to move freely with the ballast tank compartments and through access ports between compartments. For example, it is contemplated that an ROV known as “VideoRay Pro 4”, which has approximate dimensions of 37.5, 28.9, 22.3 cm (14.75, 11.4, 8.75 in), may be used to inspect ballast tanks, as discussed above.

In an aspect of the present invention, an ROV 100 is inserted into a flooded ballast tank for inspection. The underwater submersible machine readable code signs or RFID tags 104 have been previously affixed in the interior compartments of the tanks to be inspected in accordance with Classification Society recommendations. These signs can also be used in shore side tanks, refineries, tank farms, and areas of waterborne infrastructure where inspection is a necessity.

The signs 104 will be marked with a unique and readable code or sign correlated to a look up table or database stored in a computer system, as well as visual markings that coincide with the as-built plans of the vessel. The signs, each with a unique id may be read by the ROV 100 flown through the tank by a pilot or operator in a remote location, such as a deck staging area or a location within the ship's house. The pilot or operator may interface with the ROV 100 through known systems, such as computer 102, tablet or the like. The lookup table or database may be stored in the computer 102, tablet or the like or may be remote to the pilot or operator, such as in cloud storage or remote computer systems accessible through the Internet or an intranet.

The pilot will operate the ROV 100 through each tank systematically, scanning each sign as it makes its way through the various compartments of the tank. The ROV 100 may be navigated within a tank from compartment to compartment through breaks in bulkheads, manholes, lightning holes, or the like. While in each tank, the ROV 100 may transmit and/or store measured data such as tank location, wall thickness, cathodic potential, magnetic particle testing, radiographic testing method, ultrasonic shearwave testing, RFID reader, video location device, salinometer, 3-D laser scanning, long base line positioning, ultra short baseline positioning, scanning sonar positioning, still photos and video.

In one example of operation, the sign may be a bar code which may be scanned by a bar code scanner on the ROV 100, which transmits other information to the computer 102. Upon reading, the system generates a pop-up window on the operators' panel of the computer 102. The window displays information pertinent to the inspection, such as the date and time stamp of the scan, as well as the identification data for the tank-compartment scanned. The window includes a video display showing the ROV camera view, as well as various other fillable data fields, including a standard grading system for the overall condition of the compartment and a field to comment on any findings in the compartment. The window may include still camera control, such as a camera icon, to allow the operator to control a still camera on the ROV 100 to take still photos of any problem areas within the compartment; these photos can be embedded in a subsequently-generated report. Also, if any of the sensors identifies a problem, the pilot may return the ROV 100 to the problem area within the inspection.

As the ROV 100 moves through the vessel, the individual scans are be saved to a database, along with any findings or still photos of problem areas. The database may be generated by vessel, by tank, by compartment, by structure, by fixture or other area of interest according to the inspection being performed. Data can be stored in relational database or other appropriate system to allow repeated access to the information and report generation. At the end of each inspection, a report may be generated listing some or all of the scanned tags, as well as any comments and photos attached to each compartment id tag. The report may be submitted to the ship owner, the Classification Society, and a copy left onboard the vessel for input into the company specific planned maintenance system.

The management system may maintain records of all reports and monitor the inspection intervals of all enrolled vessels to ensure that it is operated within compliance. Notices can be generated by the management and sent to vessel operators as reminders pending inspections.

The system may be used to inspect any fixture or structure within a tank compartment, including the transverse bulkheads, longitudinal stringers, strength members, shell plating, web frames, doubling plates, ladders, pipelines, pump casings, bell mouths, rose boxes, sumps, heating coils, scaffolding, ladders, and pipes. The advantage is that humans are removed from the inspection process, significantly increasing the safety of the process. The process also increases the available information to the client, which results in a more complete understanding of the corrosion that is happening in the tank.

It is contemplated that the present system and method will remove subjectivity from the ballast tank inspection process. Use of the ROV 100 and sensors on-board, reports can include quantifiable data such as direct measurements, and pictures/video how the tank is corroding, moving beyond simple human visual inspection.

The possible uses of this process are within ballast tanks of ships, cargo holds or tanks of ships, and drilling platforms, and other Floating Production Storage and Offloading platforms, that require annual inspections of tanks. Municipalities may also use the system and method to measure the corrosion and thickness of land based water tanks. Specifically, municipal water tanks are often painted on the interior and when they are finished, they look great. After six months or so, if the paint did not bond to the wall, it will flake off the walls. The system and method according to the present invention facilitates investigation as to why this bonding did not happen through the corrosion measurements. When the corrosion measurement increases over time, the timing of change in the tank integrity can be identified, and in conjunction, a visual inspection of the tank wall can be performed according to the present invention to ensure that that the municipality does not pay for a paint coating that is improperly applied by a contractor and does not bond.

In these vessels, an ROV 100 equipped and operating according to the present invention may be used to measure the thickness of the steel within the tank as well as conduct remote visual inspection. Moreover, sensors attached to the tank wall may measure the cathodic potential in the tank to measure the corrosion of steel in the tank. Thus, a tank's corrosion may be tracked with the cathodic potential sensors and steel thickness measurement at various points on the tank wall.

Additionally, after steel work is performed in a water tank, sensors can be placed around weld seams to ensure the proper welding materials were used. If high cathodic potential is measured, the system provides information to evaluate whether that the corrosion is either due to the new steel, or an improperly welded seam.

In operation, which is illustrated by flowchart in FIG. 6, unique identifier tags for a particular structure or fixture to be inspected will be pre-installed and linked in a database or look up table. A suitable ROV will be deployed into the liquid filled tank. In the case of ballast water tanks in a double-hulled ship, the liquid in the tank can be water. The unique identifier tags are read either by a reader resident on the ROV or by a remote scanner from a video feed from a camera on the ROV. That is, the tags may be “seen through” the ROV camera and scanned. In some instances, the unique identifier tag may be manually scanned by an inspector if the sensor is not submerged. In absence of video feed reader, an underwater code reader may be integrated with the ROV as appropriate for environment of the inspection. During inspection, an operator may view the video feed and other sensor data in real-time remotely through a computer, tablet, smart phone or the like that is in communication with the ROV via tether or wirelessly. The operator pilots the ROY through the vessel or structure being inspected. During the process of inspection, the ROV transmits through the tethered or wireless link information including the video information and appropriate sensor data. The operator has control over the ROV to capture still photos of areas of concern or interest or even the tags via the ROY camera. The entire feed, segment of the feed, or sensor data, for each compartment or tag may be provided with a continual or a static time and date stamp as well as location data of the scanned tag or compartment. In addition, the operator may make additional notes or flags in fillable fields in an interface provided to the operator at the computer to make any comments related to the findings of scanned compartment. The system may also include vessel drawings/diagrams/CAD drawings from a Naval Architect into a visual rendering of vessel, vessel diagrams indicating tanks in green for a good rating, yellow for a fair rating and red tanks for a with poor rating, or other indication as appropriate.

When a tank is selected on a diagram, it may be expanded into larger cross section showing all compartments. If a tank includes an area rated fair or poor, the compartment containing the area of concern may be shown in red or yellow on the computer control device display. When a compartment is selected on the diagram, the display may show all historical reports (scans) in a format that allows the operator to select reports (scans) according to date of inspection. Any reports (scans) with a fair or poor rating may be highlighted in corresponding color scheme.

The present system may be used in ships, boats, potable water tanks, refineries, tank farm, municipalities, naval vessels, barges, passenger vessels, water treatment facilities, dams, reservoirs, bridges, culverts, locks, and many other areas of waterborne interest.

A system according to the present invention may include off-the-shelf or custom components integrated with ROVs and handheld scanners to streamline the inspection process, manage the conditional assessment of assets to the satisfaction of the assets governing body. The system uses technology in a way that that will improve standardization the inspection process and establish a baseline for empirical data not yet understood by taking measurements in situ over long periods of time.

In accordance with the above-described invention, humans are removed from the tank inspection process and additional information is provided to the inspectors and vessel owners that is not previously available in the inspection process.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined in the appended claims.

Having thus described in detail preferred embodiments of the present invention, it is to be understood that the invention defined by the above paragraphs is not to be limited to particular details set forth in the above description as many apparent variations thereof are possible without departing from the spirit or scope of the present invention.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the present invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. 

What is claimed is:
 1. A system for inspecting a liquid filled structure, comprising: at least one submersible identification tag fixed to a fixture within the liquid filled structure; a remotely-operated underwater vehicle (ROV), the ROV including: a video camera mounted on the ROV; a transmitter for transmitting video image data from the ROV; and an operator terminal including display screen, the operator terminal in operable communication with the ROV.
 2. The system of claim 1, wherein the ROV further comprises at least one additional sensor.
 3. The system of claim 2, wherein the at least one additional sensor is one of a ultrasonic thickness gauge, cathodic potential gauge, magnetic particle testing, radiographic testing method, ultrasonic shearwave testing method, video location device, salinometer, 3-D laser scanner, long base line positioning sensor, ultra short baseline positioning sensor, and scanning sonar positioning sensor.
 4. The system of claim 1, wherein the operator terminal is a portable computer.
 5. The system of claim 1, wherein the operator terminal is a tablet computer.
 6. The system of claim 1, wherein the ROV further comprises a still camera.
 7. The system of claim 1, wherein the submersible identification tag is a bar code sign.
 8. The system of claim 7, wherein the bar code sign is a two dimensional bar code sign.
 9. The system of claim 1, wherein the submersible identification tag is a radio-frequency RFID
 10. The system of claim 1, wherein the ROV further comprises a tag reader capable of reading the at least one submersible identification tags.
 11. The system of claim 1, wherein the operator terminal further comprises a tag reader capable of reading the at least one submersible identification tags.
 12. The system of claim 1, further comprising a wireless data connection between the ROV and the operator terminal.
 13. The system of claim 1, further comprising a hard data connection between the ROV and the operator terminal.
 14. A method for inspecting a liquid filled structure, comprising the steps of: deploying a remotely-operated underwater vehicle (“ROV”) in the liquid filled structure; generating a video signal via a video camera mounted on the ROV; piloting the ROV through locations within the liquid-filled structure; reading at least one submersed identification tag fixed within the liquid filled structure to provide an identification code; correlating the identification code with a location within the structure; displaying video from the video signal on an operator terminal; and inspecting at least one fixture within the liquid-filled structure displayed on the operator terminal and determining a rating for the fixture.
 15. The method of claim 14, further comprising generating a report including the identification code and inspection results for the at least one fixture.
 16. The method of claim 14, further comprising maintaining records of inspecting at the at least one fixture.
 17. The method of claim 14, wherein the liquid-filled structure is a ballast tank of a double-hull vessel.
 18. The method of claim 14, wherein the liquid-filled structure is liquid storage tank.
 19. The method of claim 14, wherein the liquid-filled structure is a cargo hold.
 20. The method of claim 14, wherein the liquid-filled structure is liquid transport pipe. 